Real-time implementation of a three-dimensional variational data assimilation for ROMS

Zhijin Li (1), Yi Chao (1), James C. McWilliams (2), and Kayo Ide (2)
(1) Jet Propulsion Laboratory
(2) UCLA

A three-dimensional variational data assimilation (3DVAR) scheme, which is associated with the nested Regional Ocean Modeling System (ROMS) and called ROMS-DAS, has been implemented in the U. S West coast. ROMS-DAS emphasizes the capability for predicting meso- to small-scale variations with temporal scales from hours to days in coastal oceans. To cope with particular difficulties that result from complex coastline and bottom topography, complex dynamics, and sparse observations, ROMS-DAS is incorporated with novel strategies. These strategies include the implementation of three-dimensional anisotropic and inhomogeneous error correlations, application of particular weak dynamic constraints, and implementation of efficient and reliable minimization methods. These strategies will be presented. The performance of real-time implementation of ROMS-DAS with simultaneously assimilating sea surface temperatures and heights from multiple satellites, ship reports, various temperature/salinity vertical profiles will be described. The issues on the assimilation of velocity observations from ADCP and HF radars will be discussed.